Catalytic performance of Brønsted acid sites during esterification of acetic acid with ethyl alcohol over phosphotungestic acid supported on silica
✍ Scribed by Abd El-Aziz A Said; Mohamed M M Abd El-Wahab; Alian Mohamed Alian
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 2007
- Tongue
- English
- Weight
- 246 KB
- Volume
- 82
- Category
- Article
- ISSN
- 0268-2575
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✦ Synopsis
Abstract
Different ratios of phosphotungestic acid supported on silica gel were prepared by an impregnation method with PWA loadings ranging from 1 to 30% w/w and calcined at 350 and 500 °C for 4 h in a static air atmosphere. The catalysts were characterized by thermogravimety (TG), differential thermal analysis (DTA), X‐ray diffraction, FT‐IR spectroscopy and N~2~ adsorption measurements. The surface acidity and basicity of the catalyst were investigated by the dehydration–dehydrogenation of isopropanol and the adsorption of pyridine (PY) and 2,6‐dimethyl pyridine (DMPY). The gas‐phase estrification of acetic acid with ethanol was carried out at 185 °C in a conventional fixed‐bed reactor at 1 atm using air as carrier gas. The results clearly revealed that the catalyst containing 10% w/w PWA/SiO~2~ is the most active and delivers reaction selectively to ester with 85% yield. The Brønsted acid site resulting from hydroxylation of tungsten oxide plays the main role in the formation of ester. Copyright © 2007 Society of Chemical Industry